In the hydrometallurgical industry, it is of common practice to refine metal by electrolysis in electrolytic cells especially designed for this purpose. The metals to be refined are usually conventional metals like copper, zinc, nickel or cadmium, or precious metals like silver, platinum or gold, and others.
It is also of common practice to use metal plates as anodes or cathodes or both. These metal plates weight several hundred pounds. Usually, the metal to be refined, or the metal used to carry the electric current, is in the form of plates of a given thickness, which are provided at their upper end with two laterally extending projections. Such projections facilitate gripping, handling and hanging of the plates on lateral sidewalls of the cells. These projections serve also to electrically contact or insulate the electrode.
In use, the plates which, as aforesaid, can each weight several hundred pounds, are immersed into the cells in parallel relationship and are used as anodes, cathodes or both, depending on the affinity of the metal being refined.
In order to have the electrodes positioned at the exact place, it is of common practice to place a member called “capping board” or “bus bar insulator” onto the top surface of each lateral sidewall of the cells. These capping boards are used to position the plates with respect to each other. They are also used as electric insulators between adjacent cells and/or each electrodes and/or the ground.
In practice, the capping boards are used not only as supports to position the electrodes, but also as supports to avoid damage to the masonry or concrete forming the lateral side walls of the cells during the insertion and removal of the heaving electrodes.
As aforesaid, the above mentioned insulating capping boards are used to hold the electrodes at very precise positions. They are also used in combination with electrically conductive contact bars whose purpose is to allow electrical connection between the ends of the anodes and cathodes located in the adjacent cells. Thus, the combined use of capping boards and contact bars have the particularity of allowing insulation and distribution of electric current at the same time.
To achieve proper electrical contact with the contact bar, the plates forming the electrodes are provided with support hanging legs externally projecting on their opposite upper ends. Only one end of the legs of each plate is in contact with a contact bar on one side of the cell where it is located. The other leg of the same plate is held onto the capping board located on the opposite side of the cell in such a way as to be insulated. Thus, the capping board per se plays the role of an insulator and has, for this purpose, to be made of material that is insulating.
So far, it has been of common practice to use contact bars of usually triangular cross-section, that extends over the full length of the corresponding capping board in order to connect altogether all the anodes of one cell to all the cathodes of the adjacent cell.
The problem with such contact bars is that, in the case that a short circuit would occur, such would “affect” all the electrodes which are connected altogether. Such causes the temperature of some of the metal plates forming the anodes and cathodes and the contact bar to increase and such an increase may be transmitted to the insulating capping-boards, which may then be subject to deformation. Such deformation is unacceptable since it may generate other short circuits that may propagate from one cell to another cell and which may result in the production of a refined metal with major impurity and defects.